JPH11327358A - Fixing device and image forming device - Google Patents

Abstract

(57) [Summary] [Problem] To achieve good fixing performance by performing temperature control according to the state of a heating body. SOLUTION: A fixing temperature control temperature _Td and a sheet-to-sheet temperature control temperature _Tc are determined by a thermistor output indicating a temperature of a heating element of a fixing device, and heating is performed (step 1). First temperature regulation temperature T _f
G, the time to reach the inter-sheet temperature regulation temperature _Tc
And Δt = h−g are detected (steps 2 to 4), the paper feed timing is determined based on Δt (step 5), and fixing is performed at a predetermined timing (step 6). The table for determining the paper feed timing is changed according to the state of the heating element. The rise timing to the fixing temperature _Td may be determined based on Δt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed image by heating and an image forming apparatus, and more particularly to a fixing device used for permanently fixing a toner image in electrophotography to a recording material. And a control for causing a heating element used in the fixing device to generate heat.

[0002]

2. Description of the Related Art As an image heating device used in a heat fixing device, a contact heating system such as a heat roller system and a film heating system has been widely used. In such an apparatus, a current is applied to a halogen lamp or a heating resistor to generate heat, and the toner image is heated via a roller or a film. Therefore, a method of providing a heating element by providing a pattern of a resistance heating element on a ceramic substrate, generating heat, and heating the object to be heated via a thin film is disclosed in Japanese Patent Application Laid-Open No. 63-3630.
13182. For controlling the heating element, a method of always suppressing the heat generation between the sheets even when the fixing device is cold as a countermeasure against the temperature rise in the non-sheet passing portion is disclosed in JP-A-6-149.
103.

FIG. 1 is a schematic sectional view of a film heating and fixing device. Reference numeral 2 denotes an endless heat-resistant film (heat-conducting rotating body), which is exposed to a heating body support 1 which is also a guide member for a film including a heating body. The inner peripheral length of the endless heat-resistant film and the outer peripheral length of the heating body support 1 including the heating body are larger than that of the film 2 by, for example, about 3 mm. Has a loose appearance with plenty of time.

The film 2 has a film thickness of 100 to reduce the heat capacity and improve the quick start property.
μm or less, preferably 50 μm or less 20 μm or more heat-resistant single layer of PTFE, PFA, FEP, or polyimide, polyamideimide, PEEK, PES, PP
A composite layer film in which the outer peripheral surface of S or the like is coated with PTFE, PFA, FEP, or the like can be used. In this example, a polyimide film having an outer peripheral surface coated with PTFE was used.

Reference numeral 3 denotes a heating element, which is formed by applying an electric resistance material such as Ag / Pd (silver palladium) to a substrate surface made of alumina or the like to a thickness of about 10 μm and a width of 1 to 3 mm by screen printing or the like. Glass or fluororesin is coated thereon as a protective layer 7. A pressing roller 4 forms a nip N between the heating member 3 and the film 2 and drives the film. The pressing roller 4 serves as a pressing rotating member. It is made of a good heat-resistant rubber 4-b, and is driven from an end of the metal core 4-a by means not shown.

FIG. 2 is a block diagram schematically showing a fixing control circuit (control means).

[0007] The output of the thermistor (temperature detecting means) 5 provided on the temperature control heating element 3 is A / D converted by an A / D converter 9 and taken into a CPU 10, and heated by a triac 11 based on the information. The AC voltage applied to the body is controlled by controlling the power applied to the heating body by controlling the phase and the wave number.

FIG. 3 shows a fixing control temperature when the conventional heating element energizing power is controlled. 5
When the main body has not been operated for about 6 hours, the fixing device has cooled down to approximately room temperature. Fixing control temperature Ta at that time
[° C.]. When printing is started, the heating element 3 starts to increase in temperature, and the fixing control temperature 5 also changes to Tb, Tc... Immediately before the recording material P enters the nip N, the temperature of the heating element 3 is increased to a fixing temperature Td necessary for permanently fixing the unfixed image. When the main body is completely cold, the temperature control temperature is controlled to a higher position.

With such a configuration, the input voltage AC85V,
90 g / m ² paper type, 24 mm / sec process speed,
Printing is performed in a 15 ° C. room temperature environment. In this case, the environment temperature is low, the surface quality of the paper type is poor, the paper temperature is low, and the input voltage is low. Therefore, the paper feed timing is sent to heat the fixing unit to secure the fixing performance. It is necessary. If the sheet feeding is not delayed, the temperature of the fixing device cannot be raised to the fixing temperature, and the fixing device itself is not warm, so that a fixing defect occurs. Therefore, conventionally, as a countermeasure against this, a current is supplied temporarily, and a change rate of a temperature rise immediately after the current is supplied is monitored to determine the paper feed timing. FIG. 4 shows the thermistor output when the control is performed.

FIG. 4 briefly describes a conventional method of determining the paper feed timing.

[0011] Immediately after sending the print signal, 0.5se from i
c The amount of temperature rise ΔT (| T ₂ −T
₁ |) is monitored, and the timing of paper feeding is determined based on the temperature change ΔT. Table 1 shows the correspondence table.

[0012]

[Table 1] As can be seen from Table 1, when ΔT ≧ 75 deg, paper is fed immediately. This can happen if the fuser is warm,
This is often because the input voltage is high, and when the recording material enters the fixing nip, the heating element has sufficiently warmed to the fixing temperature.

If 65 deg.ltoreq..DELTA.T <75 deg., The paper is fed after the fixing unit is warmed for 5 seconds. This is for securing the time for warming the fixing device, which is often the case when the fixing device is cold or the input voltage is low. Similarly, 45deg ≦ ΔT
<65deg, after 10sec, 25deg ≦ ΔT <45de
g, the fixing unit is heated until the inter-sheet temperature is controlled, and ΔT <2
If it is 5 deg, it is determined to be faulty and reported to the host.

A program is created based on the above table. Here, when printing is performed under the printing conditions described above, when printing is performed in the low-temperature / low-voltage mode, ΔT
= 56 deg, and the paper feed timing could be delayed for 10 seconds. And good fixability was obtained.

[0015]

However, there is a mode in which it is difficult to satisfy the fixing property in the main fixing control. This is the case when the fixing device itself is heated to some extent, such as intermittent printing. In addition, erroneous detection is also performed when the state of the thermistor or movement between different environments is performed. As one example of this occurrence, when printing is performed in the morning and only a few sheets are passed, the fixing device itself is not very warm. If intermittent printing is performed in that state, the heating element itself and the thermistor (temperature detection element) are warm, so the temperature easily rises even if power is temporarily applied to know the state of the heating element. I will. Therefore, even if it is necessary to delay the sheet feeding, the sheet is immediately fed, and as a result, a fixing failure or the like occurs.

As described above, according to the conventional method, it is difficult to accurately determine the use environment and the input voltage of the device, and it is difficult to obtain a good fixing property. In particular, erroneous detection is often performed when the fixing device itself is slightly warmed, and paper is fed at an incorrect paper feed timing, resulting in an image defect.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to realize a good fixing property by controlling a temperature according to a state of a heating body. Is to do.

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a heating member, a heat conduction rotating member that conducts heat of the heating member, and a pressure rotating member pressed against the heat conduction rotating member. And a temperature detecting means for detecting a temperature of the heating element, and a control means for controlling a heat generation state of the heating element in accordance with a detection result of the temperature detecting means. A fixing device that fixes the unfixed image by sandwiching and heating and pressing the recording material on which the unfixed image is formed, wherein the heating element is used to fix the recording material while clamping the recording material. In the fixing device for maintaining the temperature of the heating element to the fixing temperature, at least two or more heating processes different from the fixing temperature are maintained. Is set to be .

According to this configuration, in the process of raising the temperature of the heating member to the fixing temperature, the heating temperature is maintained at at least two temperatures. If the time required for the temperature rise from the temperature to the higher temperature regulation temperature is detected, this can be used as a parameter for temperature control. Since this time changes according to various states of the heating body, such as the temperature of the heating body before the temperature rise and the input voltage of the heating body, more accurate temperature control becomes possible by using this as a parameter, which is favorable. And excellent fixability can be realized.

A heat roller, a heat-resistant film, or the like can be used as the heat conduction rotating body.

Further, the heating element is set to the fixing temperature in accordance with the time required for raising the temperature from the lower temperature control temperature of the temperature raising process to the higher temperature control temperature of the higher temperature process. The timing for raising the temperature to the regulated temperature may be determined.

With this configuration, it is possible to select a timing for raising the temperature of the heating element to the fixing temperature in accordance with various states of the heating element, such as the temperature of the heating element before the temperature rise and the input voltage of the heating element. Therefore, more accurate temperature control becomes possible, and good fixing properties can be realized.

[0023] Further, a time required for raising the temperature from a lower temperature control temperature of the temperature raising process to a higher temperature control temperature of the higher temperature process among the temperature control processes of the temperature raising process and the fixing temperature of the heating element are determined. It is also possible to have at least a plurality of temperature raising timing tables that define the relationship with the timing of raising the temperature to the maximum.

In this manner, a plurality of timings for raising the temperature in accordance with various conditions, such as a case where the image is formed intermittently or a case where the image is formed immediately after the power of the apparatus is turned on (so-called "one morning state"). If the timing of temperature rise is determined by selecting a table, more precise temperature control becomes possible, and more favorable fixing properties can be realized.

Further, the recording material is fed in accordance with the time required for raising the temperature from the lower temperature control temperature of the temperature raising process to the higher temperature control temperature of the higher temperature process. The timing may be determined.

In this way, the timing of feeding the recording material can be selected according to various states of the heating body, such as the temperature of the heating body before the temperature rise and the input voltage of the heating body. A fixing operation at an appropriate temperature becomes possible, and good fixing properties can be realized.

The time required to raise the temperature from the lower temperature control temperature in the temperature control process to the higher temperature control temperature in the temperature control process, and the timing of feeding the recording material. May be provided at least in plurality.

In this manner, a plurality of feed timing tables are selected according to various conditions, such as when performing image formation intermittently or when performing image formation immediately after turning on the power of the apparatus (in the morning). If the feeding timing of the recording material is determined in this manner, the fixing operation at a more appropriate temperature can be performed, and more favorable fixing properties can be realized.

Further, the temperature control temperature in the temperature raising process includes a low temperature control temperature which is a temperature control temperature between the time when the fixing operation is performed while the recording material is sandwiched and the time when the next fixing operation is performed. It is preferred that

With this configuration, it is possible to suppress the heating by maintaining the heating element at the low temperature adjustment temperature during the fixing operation, and to increase the temperature in the heating process up to the fixing temperature adjustment temperature of the heating element. By adopting the low temperature control temperature as the temperature, the set number of the temperature raising temperature control temperatures can be reduced, so that the control means can be simplified.

Further, the heat transfer rotary member may be a heat-resistant film member.

If a heat-resistant film member is used as the heat transfer rotating member, the heat capacity can be reduced, and a quick start of the fixing device is possible.

Also, in an image forming apparatus having an image forming unit for forming an unfixed image on a recording material and a fixing unit for fixing the unfixed image on the recording material, the fixing unit may include the fixing device. It may be.

[0034] In this manner, good fixability can be obtained.
An image forming apparatus capable of forming a high-quality image can be provided.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) This embodiment will be described below.

The operation is the same as that in the case where the apparatus is used under the conditions (environment, input voltage, paper type, etc.) in the above-mentioned conventional example, and the description is omitted. Table 2 shows the inter-sheet temperature control temperature for each temperature control temperature. FIG. 5 is a flowchart showing an outline of a control procedure in the present embodiment.

When printing is performed in the morning, the fixing unit itself is at the ambient temperature of the apparatus. Table 2 shows the fixing temperature and the sheet-to-sheet temperature at that time with respect to the output of the thermistor (the temperature of the fixing device). In this embodiment, since the thermistor output before printing is Tth = 15 (° C.) as shown in the above conventional example, the target fixing temperature is 180 ° C., which is the morning temperature. The inter-sheet temperature control at this time is 160 ° C. (step 1).

[0038]

[Table 2] FIG. 6 shows the temperature and elapsed time when printing is performed under these conditions. First, start printing in the morning
At time g, the temperature reaches the first (temperature control) temperature Tf (80 ° C.) (step 2). Then, at time h, the temperature reaches the inter-sheet temperature regulation temperature Tc which is the second (temperature regulation) temperature (step 3). At this time, the difference between the time when the first temperature has reached and the time when the second temperature has been reached is detected (step 4), and the sheet feeding timing is determined according to Table 3 (feeding timing table) described later (step 5). . In this state, the heating element was heated while the heating element was being heated, and the sheet feeding was started with a delay of 6 seconds. Then, the fixing temperature Td (180 ° C.)
And fixing is performed (step 6).

[0039]

[Table 3] Table 3 will be described.

The time when the temperature reaches the first temperature Tf is monitored. This time is time g. Further, the time when the temperature reaches the second temperature Tc is also monitored. This time is time h. The sheet feed timing is determined by a value obtained by subtracting the two times (Δt = h−g).

As shown in Table 3, when .DELTA.t.ltoreq.3 (sec), sheet feeding is started immediately and printing is started. If 3 <Δt ≦ 5, wait for 2 (sec). If 5 <Δt ≦ 8, wait for 6 (sec). If 8 <Δt, wait for 15 seconds.

On the other hand, in the case of intermittent printing, the sheet feeding timing is determined using a table different from the table shown above. In the case of intermittent printing, the fixing device itself is often warmed, and in the sequence of the preceding table alone, excessive heat is supplied to the paper at the time of fixing, resulting in excessive fixing, resulting in hot offset. Also, in the case of intermittent printing, a sequence prepared based on another table must be used because the desired fixing temperature adjustment temperature is easily raised even at a low voltage.

Table 4 shows the sequence for performing intermittent printing.
It writes in.

[0044]

[Table 4] As compared with Table 3, in Table 4, the time Δt and the paper feed delay corresponding thereto are smaller. This is due to the fact that the fixing device itself is warmed as described above.

(Second Embodiment) This embodiment will be described below.

In the first embodiment, the paper feed timing is determined by the time required for the temperature of the heating element to rise in a certain temperature range, and the paper can be fed at an appropriate timing. As a result, good fixing performance was ensured, but when an input voltage higher than the rated voltage was input, the fixing device was continuously started up until the sheet was fed, or the fixed fixing temperature was maintained even after the start-up. Since heating is continued at the regulated temperature, the temperature of the fixing device itself rises, and hot offset may occur.

Therefore, in the present embodiment, the temperature control is continued at the second temperature until the paper feeding time, and the timing for raising the fixing temperature is determined based on the table shown in Table 5.

[0048]

[Table 5] FIG. 7 shows the waveform of the thermistor when performing intermittent printing.

As compared with FIG. 6, the time h to m (temperature T
It can be seen that part c) is long. Since the input voltage is large as described above, the time Δt (g to h) required for the temperature rise from the temperature Tf to Tc is very short, and thus such control is performed. Specifically, since the input voltage was 120 V, Δt = 0.8 sec. Table 5
The temperature was raised after maintaining the low temperature control for 3 seconds from the (temperature rise timing table). FIG. 8 shows a comparison between how the pressure roller warms up when this control is not performed and when it is performed. As can be seen from FIG. 8, since the pressure roller is warmed at a low temperature without rising to the fixing temperature at the time h to m, the temperature is 65 ° C. to 85 ° C.
It can be seen that the rise in temperature at was relatively slow.
Then, finally, the temperature of the pressure roller is suppressed lower than when the control of the present embodiment is not performed.
The manner in which the pressure roller warms when the control is performed is an ideal (theoretical) curve in which the ideal pressure roller temperature is plotted. Therefore, by performing the control according to the present embodiment, it is possible to obtain a good image without offset.

In addition, by monitoring the input voltage, it is possible to select a highly accurate sheet feeding timing and a temperature control start timing, and it is possible to obtain a good fixing property.

[0051]

As described above, according to the present invention,
In addition to obtaining good fixability, there is an effect that a high-quality image can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixing device according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a fixing control circuit of the fixing device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a thermistor output when conventional fixing control is performed.

FIG. 4 is an enlarged view of a thermistor output when a conventional fixing control is performed.

FIG. 5 is a flowchart showing a control procedure according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a thermistor output indicating fixing control used in the first embodiment of the present invention.

FIG. 7 is a diagram showing a thermistor output indicating fixing control used in a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a pressure roller temperature by a fixing control used in a second embodiment of the present invention.

[Explanation of symbols]

 2 Film 3 Heating Element 4 Pressure Roller 5 Thermistor 9 A / D Converter 10 CPU 11 Triac

Claims (8)

[Claims] A heating member, a heat conduction rotator that conducts heat of the heating member, a pressure rotator that is pressed against the heat conduction rotator, and a temperature detector that detects a temperature of the heating member. Control means for controlling the heat generation state of the heating element in accordance with the detection result of the temperature detection means, wherein a recording material on which an unfixed image is formed is sandwiched between the heat conduction rotating body and the pressing rotating body. A fixing device for fixing the unfixed image by heating and pressurizing, wherein the fixing device is configured to maintain the heating element at a predetermined fixing temperature when fixing the recording material. A fixing device characterized in that, in the process of raising the temperature of the heating element to the fixing temperature, the fixing device is set to maintain at least two or more temperature rising temperatures different from the fixing temperature. . 2. The fixing device according to claim 1, wherein the heating unit is configured to control the fixing temperature according to a time required for raising the temperature from a lower temperature control temperature of the temperature control process to a higher temperature control temperature of the temperature control process. 2. The fixing device according to claim 1, wherein a timing for raising the temperature to the regulated temperature is determined. 3. A time required for raising the temperature from a lower temperature control temperature in the temperature control process to a higher temperature control temperature in the temperature control process and the fixing temperature of the heating element. The fixing device according to claim 2, further comprising at least a plurality of temperature raising timing tables that define a relationship with a timing at which the temperature is raised to a maximum. 4. The recording material is fed in accordance with a time required for raising the temperature from a lower temperature control temperature in the temperature control process to a higher temperature control process in the temperature control process. The fixing device according to claim 1, wherein the timing is determined. 5. A time required to raise the temperature from a lower temperature control temperature in the temperature control process to a higher temperature control process in the temperature control process, and a timing of feeding the recording material. 5. The fixing device according to claim 4, wherein the fixing device has at least a plurality of feed timing tables that define the relationship. 6. The low-temperature control temperature, which is a control temperature between the time when the fixing operation is performed while sandwiching the recording material and the time when the next fixing operation is performed, is included in the temperature control process. The fixing device according to claim 1, wherein the fixing device is used. 7. The fixing device according to claim 1, wherein the heat transfer rotator is a heat-resistant film member. 8. An image forming apparatus comprising: an image forming unit for forming an unfixed image on a recording material; and a fixing unit for fixing the unfixed image on the recording material, wherein the fixing unit is provided. An image forming apparatus comprising the fixing device according to (1).